Cookie

方法名称	作用
Cookie(key,value)	cookie的构造函数。
setMaxAge()	设置cookie的最大存活时间。
getValue(key)	获取对应key的cookie值。
setValue(key,newValue)	修改对应key的cookie的值。
response.addCookie(cookie)	往响应中添加对应key的cookie对象。

4|3利用Cookie来实现7天免登陆

用于处理登录请求的LoginServlet:

import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet(name = "LoginServlet",urlPatterns = "/LoginServlet") public class LoginServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //登录判断逻辑 (实际开发中从请求中获取参数匹配数据库) System.out.println("login success"); //创建Cookie对象 Cookie c = new Cookie("user","admin"); //设置cookie有效期 c.setMaxAge(60*60*24*7); //添加cookie到响应中 response.addCookie(c); } }

用于作为用户主页的IndexServlet

import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; @WebServlet(name = "IndexServlet",urlPatterns = "/IndexServlet") public class IndexServlet extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取请求中所有cookie Cookie[] cs = request.getCookies(); //判断是否有cookie if(cs!=null){ String name = null; //遍历所有cookie for (Cookie c: cs) { //找到用户名称 if(c.getName().equals("user")){ name =c.getValue(); } } //在页面输出已经登录过的用户名称 response.setContentType("text/html;charset=utf-8"); if(name != null){ response.getWriter().println("user:" + name); } } } }

在浏览器中先访问LoginServlet,重新启动浏览器,访问IndexServlet可以看到之前登录的用户信息